F9 and hemophilia A: To give a recent example, recombinant activated factor VII (rFVIIa) is an endogenous serine protease that initiates the extrinsic blood coagulation cascade, and it is an alternative “bypass” treatment for hemophilia A or B patients who have become non-responders to their replacement therapy (usually due to development of ADAs against infused factor VIII (FVIII) or factor IX (FIX), respectively).